1. Field of the Invention
The present invention relates to an artificial heart pump system and a controller utilized for its control and more particularly to an artificial heart pump system where a plurality of processors are provided in the control apparatus and a load burdened in one processor is made reduced.
2. Description of the Related Art
In a conventional assisted artificial heart pump system, it was proposed a system where a sensor circuit for discriminating a levitating position of an impeller is built-in in a pump body in order to establish compatibility between a blood pump body and a controller which are used for an artificial heart (see Jap. laid-open Pat. No. 2001-327595).
Also, as a control method of a blood pump used such as for an artificial heart and for an artificial heart and lung where of the blood pump is assisting or completely displacing a living-body heart by being bypass connected, there was known a method in which the current flowing in the blood pump is controlled to be constant so as to restrain a flow rate change of the blood pump in a small range in response to a variation of a pressure load (see Jap. laid-open Pat. No. 9-56812).
Further, there was known a centrifugal type blood pump apparatus which is an control apparatus of a blood pump used for an artificial heart and lung apparatus where a relation between a motor current of a blood pump apparatus and a motor rotational speed and discharging flow rate is memorized beforehand such that a current amount control of a motor, a levitating position control of an impeller, a rotation torque control of the impeller, calculation of a liquid viscosity and the like are performed according to an instruction from a processor (CPU) in the controller (see Jap. laid-open Pat. No. 11-76394).
However, the controllers used for the artificial heart pump system which were described in these conventional technologies did not have a processor, were all formed by analog circuits, only a monitor was controlled by a processor even if a processor was included and the control of a motor or a bearing thereof was performed by analog circuits. Also, with respect to the controller used for these pump control apparatuses, all controls for a liquid pump and a display means were performed only by one CPU (processor).
FIG. 1 shows an example of a conventional and portable type artificial heart pump system. In this artificial heart pump system, a centrifugal type rotary blood pump 50 which has an impeller inside is implanted inside a human body. Then, a controller 51 and two batteries 52 and 53 for supplying electric power thereto are held externally in a portable manner. A display unit 54 for user interface is provided in the controller 51.
The blood pump 50 is implanted inside the human body and connected to the portable controller 51 through a cable 55 which passes through a skin.
FIG. 2 is a block constitutional diagram showing an inside constitution of a controller normally used in a conventional artificial heart pump system. The artificial heart pump system is composed of a blood pump 100 (corresponding to the blood pump 50 in FIG. 1) which is implanted inside a human body, a controller 101 (corresponding to the controller 51 in FIG. 1) for controlling an operation status of the blood pump 100, and a battery 102 (corresponding to batteries 52 and 53 in FIG. 1) for supplying electric power to a power supply circuit of the controller 101.
Then, controller 101 is provided with a processor 103 which supervises a control of the whole controller; a memory device 104 which saves observation data of an operation status of the blood pump 100; an operation condition of the blood pump or the like; a magnetic levitating control circuit 105 for magnetically float-controlling the impeller which consist of the blood pump 100; a motor driving circuit 106 for drive-controlling the motor; a power supply circuit 107 for supplying electric power to the processor 103, the memory device 104, the magnetic levitating control circuit 105 and the motor driving circuit 106; a liquid crystal display unit (LCD) 108 for displaying a rotational speed of the impeller of the blood pump, a blood flow rate, a discharging pressure or the like; an LCD light emitting device 109 for displaying whether the operation of the blood pump and aforesaid controller is normal or abnormal; a buzzer 110 for announcing an abnormality of the blood pump and aforesaid controller; and an instruction button 111 for instructing to the processor 103, a change of the pump activation, a change of the LCD displaying content, a release of an abnormal status or the like.
Hereinafter, the operation of the conventional artificial heart pump system shown in FIG. 2 will be explained. An impeller provided inside the blood pump 100 is controlled by the magnetic levitating control circuit 105 so as to be levitating magnetically and at the same time controlled by the motor driving circuit 106 so as to rotate in a stable rotational speed. The rotational speed of the motor for rotating the impeller will be set by a medical staff taking a blood viscosity, a discharging flow rate or the like of a patient into consideration and is normally set to be in a range of 1300 rpm to 2200 rpm.
The processor 103 receives signals from the magnetic levitating control circuit 105 and motor driving circuit 106 and make the memory device 104 store necessary information and at the same time makes the liquid crystal display device (LCD) 108 display the operation status of the blood pump 100. The displayed contents of the LCD 108 are a rotational speed of the impeller, a blood flow rate, a discharging pressure of the blood pump and the like.
In a case when an abnormality of the blood pump 100 is detected, the processor 103 makes the displayed color of the LED light emitting device 109 change from green to red and at the same time makes the buzzer 110 activated so as to generate warning sounds.
Also, in the memory device 104, not only the operation status of the blood pump 100 is recorded but also a condition setting for activating the blood pump is stored beforehand such that the processor 103 reads in the setting value stored in the memory device 104 and is to control the operation status of the blood pump 100.
However, in the conventional artificial heart pump system shown in FIG. 2, the processor 103 possessed by the controller 101 is only one. Consequently, all of the processes in the controller 101 should be performed by the processor 103.
More specifically, the processor 103 should perform all of the processes such as the magnetic levitating control of the pump 100, the motor rotational speed control, the data saving process, the data displaying process and the alarm rumbling process.
This means that a very heavy load is requested to the processor 103 and a processor of a high performance having a performance which can execute all of them should be installed. In other words, a high cost is requested for the processor.
Also, in a case when all the processes are performed by one processor 103 in this manner, the software operated on the processor 103 becomes complicated and consequently, productivity and maintainability will be lowered such that a large amount of cost is to be necessary for keeping them.
Further, in a case when the processor 103 stops caused by some kind or another trouble, the controller 101 cannot continue the above mentioned all processes. In this stage, the controller 101 stops its function and there might happen that even a warning notice cannot be emanated.
In an artificial heart pump system, the most important thing is to continue the pump operation safely and it was necessary to provide a processor of a high performance for securing security in aforesaid conventional artificial heart pump system which uses a single processor.
FIG. 3 shows a ventricular assist device (system) described in the specification of U.S. Pat. No. 6,183,412. In this ventricular assist device (system), a rotational pump 60 and a flowmeter 61 are implanted inside a human body. Then, units provided outside of the body of a patient are a portable type controller 62, a clinical data collecting device 63 for collecting clinical data and a home support system 64 of the patient.
[Cited Patent References]
                (1) Jap. Laid-open Pat. No. 2001-327595        (2) Jap. Laid-open Pat. No. 09-056812        (3) Jap. Laid-open Pat. No. 11-076394        (4) U.S. Pat. No. 6,183,412        